Accelerated Reactions in Droplets and Thin Films: Surface Effects and Analytical Implications

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With support from the Chemical Measurement and Imaging Program in the Division of Chemistry, Professor Graham Cooks and his group at Purdue University are working to explain and exploit a startling but simple fact: the speed of many chemical reactions increases dramatically as the volume of the reacting mixture decreases. Because of this, reactions in microdroplets can easily be thousands of times faster than the same reactions in jars, barrels or industrial vats. This may offer an alternative to the use of expensive chemical catalysts to save time and energy. Research in the Cooks group is focused on understanding the role of the droplet interface in accelerating reactions, particularly those that are useful in various analytical measurements. Among other potential applications are studies of the shelf life of pharmaceuticals, and detailed examination of fast biochemical reactions that occur within living cells. The project provides training in advanced instrumentation and precision chemical measurements, and prepares graduate students to contribute to the US workforce in a field with strong industrial and national security ties. A range of methods will be deployed to transfer the results of the research and strengthen the training aspect of the program, including strong industrial interactions, focused short training courses, inclusion of undergraduates in research, and collaborative research efforts involving regional institutions with strength in analytical chemistry.The research objectives of this proposal are to discover and characterize ways to exploit accelerated reactions (including derivatization) for chemical analysis in droplets and other confined volumes, and to elucidate the mechanisms that increase reaction rate constants. The search for mechanistic knowledge focusses on kinetic studies of surface vs. bulk reactions as a function of droplet size and reagent concentration. Mass spectrometry can benefit from as well as probe these reactions. It is the main measurement tool, along with interfacial vibrational spectrometry. Other target applications come from both academic and industrial settings. Examples include chemical reactions involving non-covalent clusters of amino acids and peptide bond formation.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.